RESIN MOLDED ARTICLE WITH BOSS OR RIB AND APPARATUS AND METHOD FOR INJECTION MOLDING OF THE ARTICLE

摘要

PROBLEM TO BE SOLVED: To prevent sink marks from being generated by providing a projection around a boss or a rib on the back surface side of a molded article. SOLUTION: In an injection molding apparatus for a resin molded article with a boss or a rib, a means for ejecting a compressed gas into a mold is provided and an inlet hole 10 for the compressed air is provided on the cavity face of the mold in the neighborhood corresponding to the boss or the rib on the back surface side of the molded article. In addition, recessed parts 92 for preventing the compressed gas from diffusing by the wall of a filled resin are provided on a part corresponding to the boss or the rib of the cavity face of the mold and in the neighborhood surrounding the inlet hole. Pref., projected parts are furthermore provided by adjoining to the recessed parts 92 of the cavity face of the mold and in the neighborhood surrounding them. These recessed parts 92 correspond to projected parts of the molded article and the projected parts 94 correspond to drawn parts.